PDF/A (Portable Document Format for Archiving) is an ISO-standardized version of the PDF format designed specifically for the long-term preservation of electronic documents.
If you have ever tried to submit a document to a government portal, a court system, or a university thesis repository, you may have been explicitly required to provide a PDF/A rather than a standard PDF.
Why Was PDF/A Created?
A standard PDF is excellent for sharing documents today, but it is not guaranteed to work flawlessly 50 years from now.
Standard PDFs often rely on the computer opening them to provide certain resources. For instance, a standard PDF might link to a font installed on your PC rather than storing the font itself. It might also contain audio, video, or JavaScript.
If you try to open that standard PDF decades later on a completely different operating system that lacks those fonts or doesn't support that ancient JavaScript engine, the document will break or look incorrect.
The PDF/A standard was created to eliminate these dependencies. The core philosophy is that a PDF/A must be 100% self-contained.
The Strict Rules of PDF/A
To ensure a document can be opened and look identical forever, the PDF/A standard strictly forbids features that could compromise future readability.
If a file violates these rules, it is not a valid PDF/A:
- All Fonts Must Be Embedded: The file must contain the actual font data for every character used in the document.
- No Encryption: The file cannot be password-protected or restricted. An archivist must always be able to access the content.
- No Audio or Video: Multimedia is banned because the software required to play it might become obsolete.
- No JavaScript: Executable code is not allowed.
- Color Spaces Must Be Defined: The file must contain specific instructions on how to render colors independently of the device's screen or printer settings.
The Different Versions of PDF/A
The standard has evolved over time, resulting in different versions (PDF/A-1, PDF/A-2, PDF/A-3, PDF/A-4).
- PDF/A-1: The original standard (2005). Extremely strict. Does not support transparency (layers) or attachments.
- PDF/A-2: Introduced in 2011. Adds support for image transparency, JPEG 2000 compression, and allows smaller PDF/A files to be embedded within a master PDF/A.
- PDF/A-3: Similar to A-2, but crucially allows any file format (like an Excel spreadsheet or an XML file) to be embedded as an attachment.
Additionally, you will often see letters appended to the version (e.g., PDF/A-1b or PDF/A-2u):
- b (Basic): Ensures the document visually looks correct.
- u (Unicode): Ensures the text is Unicode compliant, meaning it can be reliably searched and copied.
- a (Accessible): The strictest level. Includes 'u' and 'b', but also requires the document to be tagged for screen readers and accessibility devices.
How to Create a PDF/A
Most modern word processors and PDF editors allow you to save as PDF/A. In Microsoft Word, when saving as a PDF, click Options, and check the box for "PDF/A compliant".
You can also use ToolzStack's Document Converter to convert standard PDFs and Office documents into compliant PDF/A files for archiving.
Related guides: PDF vs PDF/A · What is a PDF File?